Vascular plugs have been known for a number of years. Many are in the form of a device which is implanted within a vessel of a patient and have a structure which closes off the vessel so as to occlude blood flow. Occluders of the plug type are preferable over more traditional forms of occlusion, such as vascular constrictors, which generally require an invasive medical procedure. Vascular plugs, on the other hand, can be deployed endoluminally in a significantly faster and less traumatic medical intervention.
Vascular plugs may be designed or used to provide temporary occlusion, for example to be effective only for the duration of a medical procedure or during a period of treatment. Occlusion may also be permanent, in which case the occluder will be left within the patient indefinitely.
There are two primary types of occluding vascular plug. The first promotes embolization within the vessel, for instance by slowing the flow of blood through the device, in some cases with the addition of embolization promoters. Such devices do not produce immediate occlusion of the vessel as they rely upon the formation of sufficient blood clotting to act as the occluding barrier. Thrombosis in sufficient amount to occlude can take hours, days or even weeks in some instances.
Another type of vascular plug has an impervious element, typically a membrane, which extends across the diameter of the vessel to create an instantaneous barrier to blood flow. In many cases such immediate occlusion is preferable. However, it is difficult to counter reliably the full force of the blood flow, leading to risk of migration of the device, loss of positional orientation, or failure to achieve a full seal against the vessel wall and thus in failure of the device. Furthermore, some such devices can fail to deploy properly in the vessel, leading them to being ineffective from the start.
Some examples of known vascular plugs can be found in U.S. Pat. No. 5,645,558, U.S. Pat. No. 5,683,411, U.S. Pat. No. 6,063,113, US-2008/262,518, US-2009/099,647 and WO-10/085,344.